In present LTE (Long Term Evolution) system, the sounding of uplink channel is completed through sounding signal, which is sent through the last symbol of terminal at SRS (Sounding Reference Signal) subframe. The base station can obtain the uplink channel information and thus conduct resource scheduling and measurement for the uplink transmission, including measurement of RI (Rank Indication)/PMI (Precoding Matrix Indicator)/CQI (Channel Quality Indication), etc. SRS in LTE system is periodically sent, that is, sounding signal is sent continually by terminal in a certain period till getting into the status of no data transmission. The parameters of periodic SRS are configured through high layer, including CS (Cycle Shift), bandwidth, frequency hopping parameter, period and position of sending subframe, etc. of SRS.
Due to long scheduling period and low scheduling efficiency, the periodic SRS frequently occupies many physical resources. In particular in LTE-A (Long Term Evolution Advanced) system, UE (User Equipment) is frequently required to send multi-antenna SRS simultaneously, thus causing much higher resource consumption. To improve SRS resource utilization and reduce SRS resource consumption, aperiodic SRS transmission is introduced into LTE-A system. Unlike the periodic SRS, aperiodic SRS is dynamically activated by the base station. After activation, the terminal shall send sounding signal once only instead of periodically. Through aperiodic sounding, the base station can more flexibly acquire the channel information required and close or reduce transmission of the periodic SRS when it is available so as to reduce physical resource consumption of SRS.
Single-antenna port transmission and multi-antenna port transmission can be adopted for aperiodic SRS. For the latter, the base station transmits aperiodic SRS signal on all transmitting antennae simultaneously.
According to present conclusions, aperiodic SRS is triggered by one bit or some bits in DCI (Downlink Control Information) format for scheduling the uplink/downlink transmission in PDCCH (Physical Downlink Control Channel).
Supposing aperiodic SRS is triggered at the Nth subframe, aperiodic SRS will be sent at the nearest one or several SRS subframes after 4 subframes. Generally such timing proceeds with subframe as unit. Cell-level parameters configuration of the periodic SRS are multiplexed for configuring time domain resource of aperiodic SRS while configuration parameters, including bandwidth, starting position, etc. of aperiodic SRS may be indicated by high layer signaling or by certain special DCI format. There is no special subframe in FDD (Frequency Division Duplexing) system, each subframe can be SRS subframe and there is one sounding symbol at most, so if aperiodic SRS is triggered, the sounding will be conducted according to configuration parameters in sounding symbol on corresponding SRS subframe based on the timing. For TDD (Time Division Duplexing) system, there are special subframes and UpPTS (Uplink Pilot Time Slot) may have two symbols that can be used for sounding, so if aperiodic SRS is triggered and transmitted in the special subframes, additional standardization will be required for transmitting aperiodic SRS in two sounding symbols to determine which symbol or symbols are used for transmitting aperiodic SRS. The diagram of TDD system frame structure in the present technology is shown in FIG. 1.
In prior art, no technical solution can solve the problems above. If simply based on the present conclusions, the symbol of the special subframe on which SRS is sent will be undeterminable.